Extrasensory Perception

Extrasensory perception (ESP) is the most common term for a number of related claims, such as clairvoyance (knowledge of events other than by the senses), telekinesis (affecting events other than by the body), and precognition (knowledge of events before they happen). Although such claims [Page 412]go back many centuries, the modern period began with the founding of the (British) Society for Psychical Research in 1882. The founders were prominent intellectuals who were motivated to find evidence for phenomena that materialism could not explain, including life after death. Thus, much of the work in this area has a quasi-religious motivation. This entry describes the phenomena attributed to extrasensory perception and the controversy surrounding these phenomena.

The history of this area is one of repeated claims based on some methodology, followed by failures to replicate. Among the prominent workers have been J. B. and Louisa Rhine, who conducted laboratory work with card guessing in the United States during the 1940s. In England, S. G. Soal performed similar studies about the same time. The methodological weaknesses in this research led to much controversy.

More recent research has included the Ganzfeld situation, in which an isolated individual attempts to send information about a target to the subject in a type of sensory isolation effected by putting half a Ping-Pong ball over each eye. Also, Robert Jahn conducted many studies in which subjects attempted to affect the output of random number generators. These two lines of work have produced large data sets that have been analyzed using meta-analysis, a method of considering many separate studies together. One problem with such research comes from what is called the law of truly large numbers. As Percy Diaconis and Fred Mosteller point out, when a sample becomes extremely large, extremely rare events tend to happen. In the present case, tiny effects caused by design flaws that would be inconsequential in ordinary research could be responsible for statistically significant results when the data set becomes extremely large. In the usual sorts of research, researchers study larger effects so that experimental design and methodology are not so critical.

These studies are only a small part of a large number that have been published over many years. The literature as a whole provides inconsistent evidence of paranormal effects, indicating the existence of a file-drawer problem: Investigators conduct a great many studies but publish mostly those that give positive results.

The judgment of the scientific community concerning the validity of the field of ESP may be seen in the 1988 report of the U.S. National Academy of Sciences that found no justification for the belief in parapsychological phenomena based on 130 years of research.

It is significant that the research in ESP has been conducted largely by people with no particular expertise in sensory processes and perception, the areas of research most closely related to the field. Thus, the typical studies have various flaws that would be avoided by those with relevant training. For example, researchers Russell Targ and Hal Puthoff employed a so-called soundproof room to isolate their subject, Uri Geller, who was famous for bending spoons and reproducing figures sketched by others. Targ and Puthoff were apparently unaware that the sound attenuating properties of such rooms are far from total and that it would be a simple matter to communicate by ordinary means through the walls. In fact, Geller's assistant was outside the room during the session, and evidently communicated to Geller what he should draw.

...